NUCLEAR FISSION

NUCLEAR FISSION

1. NUCLEAR FUSION

   • the joining of small atomic nuclei, two light nuclei (e.g hydrogen) can be joinedd to create a larger nucleus
     • the process releases allot of energy- all energy released in stars is from fusion so people are attempting to develop fusion reactors to create electricity as they would create so much
       • fusion doesn't leave radioactive waste behind like fission and there's plenty of hydrogen around to use as a fuel
         • the major problem is fusion can only take place at really high temperatures, 10,000,000 degrees
           • hydrogen can't be held at high temperatures and pressures needed for fusion in an ordinary container an extremely strong magnetic field is needed
             • a few experimental fusion reactors exist however none are generating electricity at the moment they are using more power to heat them up than the reactor can produce

2. splitting up big, atomic nuclei

3. Nuclear power stations generate electricity using nuclear reactors where controlled chain reactions take place in which atomic nuclei split up and release energy in the form of heat which is then used to heat water and create steam which drives a steam turbine connected to an electricity generator the "fuel" that's split is usually uranium - 235 though sometimes plutonium - 239 is used or both

   • nuclear reactor, controlled chain reaction(uranium-235 or plutonium-239)
     • atomic nuclei split, energy (heat) released
       • used to heat water
         • steam drives turbine
           • electricity generated
   • The chain reactions:
     • for fission to happen a slow moving neutron must be absorbed into a uranium or plutonium nucleus, the additional neutron causes the nucleus to become unstable so the nucleus splits
       • Each time a 'U' or 'Pu' nucleus splits up two or three neutrons are "spat out" which may hit another nucleus causing it also to split thus keeping the chain reaction going
         • when a large atom split in two two new smaller nuclei will form the new nuclei are usually radioactive due to having the "wrong" number of neutrons in them
           • a nucleus splitting(fission) gives out allot of energy lots more than any chemical reaction nuclear processes release allot more energy than chemical ones hence nuclear bombs are more powerful than ordinary bombs which rely on chemical reactions
             • the main problem with nuclear power is waste disposal the products left over from nuclear fission are highly radioactive so are very difficult and expensive to dispose of
             • nuclear fuel is cheap but overall cost is high due too power plant cost and final decomissioning (dismantling a nuclear power plant safely takes decades)
             • nuclear power plant also means risk of radiation leaks or disaster (e.g chernobyl)